Regex

Explore the power of regular expressions

Introduction

Name	Preview	Code	Difficulty
Matching Specific String	Match a specific string using regex.	Python	Easy
Matching Anything But a Newline	Use [.] in the regex expression to match anything but a newline character.	Python	Easy
Matching Digits & Non-Digit Characters	Use the expression \d to match digits and \D to match non-digit characters.	Python	Easy
Matching Whitespace & Non-Whitespace Character	Use \s to match whitespace and \S to match non whitespace characters in this challenge.	Python	Easy
Matching Word & Non-Word Character	Use \w to match any word and \W to match any non-word character.	Python	Easy
Matching Start & End	Use the ^ symbol to match the start of a string, and the $ symbol to match the end characters.	Python	Easy

Character Class

Name	Preview	Code	Difficulty
Matching Specific Characters	Use the [ ] expression to match specific characters.	Python	Easy
Excluding Specific Characters	Use the [^] character class to exclude specific characters.	Python	Easy
Matching Character Ranges	Write a RegEx matching a range of characters.	Python	Easy

Repetitions

Name	Preview	Code	Difficulty
Matching {x} Repetitions	Match exactly x repetitions using the tool {x}.	Python	Easy
Matching {x, y} Repetitions	Match between a range of x and y repetitions using the {x,y} tool.	Python	Easy
Matching Zero Or More Repetitions	Match zero or more repetitions of character/character class/group using the * symbol in regex.	Python	Easy
Matching One Or More Repetitions	Match zero or more repetitions of character/character class/group with the + symbol.	Python	Easy
Matching Ending Items	Match the end of the string using the $ boundary matcher.	Python	Easy

Grouping and Capturing

Name	Preview	Code	Difficulty
Matching Word Boundaries	Using \b to match word boundaries.	Python	Easy
Capturing & Non-Capturing Groups	Creating capturing and non-capturing group.	Python	Easy
Alternative Matching	Matching single regex out of several regex.	Python	Easy

Backreferences

Name	Preview	Code	Difficulty
Matching Same Text Again & Again	Match the same text as previously matched by the capturing group.	Python	Easy
Backreferences To Failed Groups	Backreference to a capturing group that match nothing.	Python	Easy
Branch Reset Groups	Alternatives having same capturing group	Perl	Easy
Forward References	Back reference to a group which appear later in regex.	Java	Easy

Assertions

Name	Preview	Code	Difficulty
Positive Lookahead	A positive lookahead asserts the regex to match if the regexp ahead is matching.	Python	Easy
Negative Lookahead	It asserts the regex to match if regexp ahead is not matching.	Python	Easy
Positive Lookbehind	It asserts the regex to match if regexp behind is matching.	Python	Easy
Negative Lookbehind	It asserts the regex to match if regexp behind is not matching.	Python	Easy

Applications

Name	Preview	Code	Difficulty
Detect HTML links	Use Regular Expressions to detect links in a given HTML fragment.	Python	Medium
Detect HTML Tags	Given N lines of HTML source, print the HTML tags found within it.	Python	Easy
Find A Sub-Word	Use RegEx to count the number of times a sub-word appears in a given set of sentences.	Python	Easy
Alien Username	Validate the usernames from an alien planet.	Python	Easy
IP Address Validation	Validate possible IP Addresses with regex.	Python	Easy
Find a Word	Find a given word in a sentence using regex special characters.	Python	Medium
Detect the Email Addresses	Use Regular Expressions to detect the email addresses embedded in a given chunk of text.	Python	Medium
Detect the Domain Name	Use Regular Expressions to detect domain names from a chunk of HTML Markup provided to you.	Python	Medium
Building a Smart IDE: Identifying comments	A Text Processing Challenge. Identify the comments in program source codes.	Python	Medium
Detecting Valid Latitude and Longitude Pairs	Can you detect the Latitude and Longitude embedded in text snippets, using regular expressions?	Python	Easy
HackerRank Tweets	Write a regex to identify the tweets that has the string hackerrank in it	Python	Easy
Build a Stack Exchange Scraper	Use Regular Expression to Scrape Questions from Stack Exchange.	Python	Easy
Utopian Identification Number	Can you use regular expressions to check if the Utopian Identification Number is valid or not?	Python	Easy
Valid PAN format	Use regex to determine the validity of a given set of characters.	Python	Easy
Find HackerRank	Write a regex to find out if conversations start/end or both start and end with hackerrank	Python	Easy
Saying Hi	Use a regex to print all the lines that start with “hi “ but are not immediately followed by a ‘d’ or ‘D’.	Python	Easy
HackerRank Language	Use regex if an api request has a valid language string set or not	Python	Easy
Building a Smart IDE: Programming Language Detection	You are provided with a set of programs in Java, C and Python and you are also told which of the languages each program is in. Now, given a program written in one of these languages, can you identify which of the languages it is written in?	Python	Medium
Split the Phone Numbers	This problem introduces you to the concept of matching groups in regular expressions.	Python	Easy
Detect HTML Attributes	Use Regular Expressions to detect HTML Attributes corresponding to various tags.	Python	Easy
The British and American Style of Spelling	Use regular expression to find the count of a given word that ends with either ze or se	Python	Easy
UK and US: Part 2	Use regular expression to count the number of occurrences of a given word with either our or or in it.	Python	Easy